The present invention relates to a tea product, more specifically, certain black leaf teas that resemble orthodox processed tea but possess infusion characteristics more similar to that of CTC processed tea.
Leaf tea may be prepared as green leaf tea or black leaf tea. Generally, to prepare black leaf tea fresh green leaves of the plant Camellia sinensis are withered (subjected to mild drying), comminuted, fermented (in which process enzymes in the tea leaf use atmospheric oxygen to oxidize various substrates to produce brown-coloured products) and then fired (to dry the tea leaves). Green leaf tea is not exposed to the fermentation process. Partial fermentation may be used to produce intermediate-type teas known as xe2x80x9coolongxe2x80x9d tea.
Conventional wisdom dictates that in black tea manufacture tea must be macerated in some way to liberate the fermentative enzymes and their substrates within the leaves. One can macerate tea in many ways but broadly speaking there are two main mechanised methods for doing this.
The first, called xe2x80x9corthodox manufacturexe2x80x9d, involves rolling pre-weighed batches of withered tea leaves prior to fermenting, firing and drying steps. So called xe2x80x9corthodox teaxe2x80x9d is typically characterised by withered leaf portions that are aesthetically pleasing to many but produce lighter liquors due to less extensive fermentation.
The second method is the most popular of a number of non-orthodox, continuous methods that involves using a machine resembling a mangle that cuts, tears and curls tea leaves. The original machine was invented by W. McKercher in 1930 and is commonly referred to as a CTC (cut-tear-curl) machine. The finely cut product is known generically as xe2x80x9cCTC teaxe2x80x9d and is characterised by a fast infusion rate and strong colour. This method tends to produce tea that is more consistent and uniform in quality than the orthodox method.
Both orthodox and CTC machines are often used in conjunction with a Rotorvane machine, which minces withered tea leaves. These methods and their history and role in tea manufacture are described in xe2x80x9cTea: Cultivation to Consumptionxe2x80x9d edited by K. C. Willson and M. N. Clifford, Chapman and Hall, 1992.
Generally speaking consumer preference for either orthodox or CTC tea is a matter of national or regional culture. In some countries the visual appearance and texture of leaf tea are important indicators of quality, larger leaf particles being associated with higher quality. In Western markets tea is increasingly purchased in filter paper bags and the colour of the infused product tends to be more important.
Some consumers however want the best of both worlds; i.e. a leaf tea that looks and feels like orthodox processed tea but has the liquor characteristics of a fuller fermented CTC processed tea. Unfortunately there is no commercially available tea manufacturing equipment that can deliver such a leaf tea.
In response to those needs, the present inventors have developed a black leaf tea that resembles orthodox processed tea but infuses like CTC processed tea.
In our co-pending international patent application PCT/EP99/00775 whole tea leaves are subjected to a heat shock at a temperature and for a duration that is sufficient to initiate fermentation, and enabling the tea to ferment for a time and at a temperature that is sufficient to achieve desired liquor properties. In our co-pending European patent application EP 98306543 whole leaf tea is impregnated tea leaves with liquid carbon dioxide within a pressure vessel, depressurising the vessel at a rate that is sufficient to freeze the liquid carbon dioxide, applying sufficient heat to cause the frozen carbon dioxide to sublime and consequently initiate fermentation within the leaves, allowing the tea to ferment for a time that is sufficient to achieve desired liquor properties, and drying the fermented product to yield the whole leaf tea.
Both methods can be used to make black leaf tea that resembles orthodox processed tea but has the infusion characteristics of CTC processed tea. A third method is described in our co-pending United Kingdom patent application GB 0010315.0.
The present inventors have investigated the product parameters of some of the most preferred products of the aforementioned methods and found they can be characterised as products per se, that is, irrespective of their method of manufacture.
In broad terms the present invention relates to black leaf tea that has the appearance of orthodox processed black tea but is characterised in that it has the infusion characteristics of CTC processed black leaf tea.
Orthodox appearance can be determined by an expert tea taster, a trained panel or image analysis. Preferably the leaf tea comprises whole leaf grades or leafy brokens.
The average length of the leaf tea is preferably at least three times the average width of the tea, especially or at least about 5% of the tea particles have a D-circle perimeter ratio of 1.6 or greater.
CTC infusion character can be determined by an expert tea taster, both in the presence or absence of milk, both qualitatively and quantitatively on a suitable industry scale.
A black tea of the present invention when infused in freshly boiled deionised water at a concentration of 10 g/l for 3 minutes preferably provides an infusion that has an a* value of 12 or greater and a b* value of 75 or greater, more preferably an a* value of 14 and greater and a b* value of 80 or greater, but especially an a* value of 16 and greater and a b* value of 85 or greater.
The black leaf tea preferably infuses in freshly boiled water at a rate in excess of that of the equivalent mass of the same tea of a comparable size that has undergone orthodox processing, but preferably at least as fast as the equivalent mass of the same tea that has undergone CTC processing.
xe2x80x9cTeaxe2x80x9d for the purposes of the present invention means leaf material from Camellia sinensis or Camellia assamica. It also includes rooibos tea obtained from Aspalathus linearis however that is a poor source of endogenous fermenting enzymes. xe2x80x9cTeaxe2x80x9d is also intended to include the product of blending two or more of any of these teas.
xe2x80x9cLeaf teaxe2x80x9d means tea that contains one or more tea origins in an uninfused form.
xe2x80x9cBlack leaf teaxe2x80x9d means substantially fermented leaf tea.
xe2x80x9cWhole leaf teaxe2x80x9d includes tea leaves that are substantially intact, that is leaves that have not been macerated whether that be comminuted by cutting etc, disrupted by rolling, or by some other means. It could conveniently include single leaves, a cluster of leaves or the traditional two leaves and a bud. Substantial leaf fragments that are otherwise unmacerated may well behave like intact leaves and thus for the purposes of this invention they should be considered as xe2x80x9cwhole leaf teaxe2x80x9d too.
For the avoidance of doubt the word xe2x80x98comprisesxe2x80x99 is intended to mean including but not necessarily xe2x80x9cconsisting ofxe2x80x9d or xe2x80x9ccomposed ofxe2x80x9d. In other words the listed steps or options need not be exhaustive.
The present invention relates to certain leaf black teas that resemble orthodox processed tea but infuse rapidly like CTC processed tea.
Whole leaf tea, it seems, withered or not, will not spontaneously ferment. It must be triggered. The applicant has found this can be achieved by the methods described in the aforementioned international patent application PCT/EP99/00775, European patent application EP 98306543, and United Kingdom patent application GB 0010315.0. The specifications of each are incorporated into the present specification by reference.
The present inventors have investigated the product parameters of some of the most preferred products of the aforementioned methods and found they can be characterised as products per se, irrespective of their method of manufacture.
The black leaf tea of the present invention can be characterised with respect to its orthodox appearance and CTC infusion character as will be described in the ensuing pages with reference to the accompanying drawings.
In the drawings:
FIG. 1 illustrates the predominant leaf tea shapes that were used to train a panel to distinguish between various leaf appearances. This is described in detail in Example 2.
FIGS. 2a to 2d are histograms showing the frequency distribution of D-circle perimeter ratio (DCPR) values for various teas examined in Example 3. These can be used to distinguish between orthodox and CTC leaf appearances. FIG. 2a represents the frequency distribution of DCPR values less than 1.2. FIG. 2b represents the frequency distribution of DCPR values between 1.2 and 1.39. FIG. 2c represents the frequency distribution of DCPR values between 1.4 and 1.59. FIG. 2d represents the frequency distribution of DCPR values of 1.6 or greater.
FIG. 3a shows the sample that was used in Example 4 to analyse the appearance of teas and generate characteristic xe2x80x9cfingerprintsxe2x80x9d from which one can also differentiate orthodox and CTC teas.
FIG. 3b illustrates how the equipment used in Example 4 was set up to analyse the appearance of teas and generate the aforementioned xe2x80x9cfingerprintsxe2x80x9d.
FIGS. 4a to 4c show the characteristic fingerprints of three samples of known orthodox manufactured teas that were generated using the method described in Example 4.
FIGS. 5a to 5c show the characteristic fingerprints of three samples of known CTC manufactured teas that were generated using the method described in Example 4.
FIGS. 6 show the characteristic fingerprint of a sample of a black leaf tea of the present invention that was generated using the method described in Example 4.
FIG. 7 is a graph of a* versus b* colour values of various teas of comparable size measured in Example 5 that shows the black leaf teas of the present invention produce infusions that are more typical of CTC manufactured teas than orthodox manufactured teas.
FIG. 8 is a graph of tea quality versus colour values of non-milked infusions of various teas as determined by an expert tea taster in Example 6.
FIG. 9 is a graph of tea quality versus colour values of milked infusions of various teas as determined by an expert tea taster in Example 7.